A mobile node (MN) using mobile IP (see Non-Patent Document 1 cited below. The mobile IP may also be referred to as CMIP below.) registers a care-of address (CoA) as a destination address with a home agent (HA) managing the home address (HoA) of the mobile node, enabling a request for forwarding, to the CoA, of packets destined to the HoA. In this specification, a mobile terminal capable of performing communication using a wireless communication function while moving is called a mobile node (MN). In other words, the MN in this specification does not always need to implement mobile IP.
Further, if the MN can register two or more CoAs in association with one HoA at the same time, the MN having two or more interfaces (which may be abbreviated as “IF” below) can register two or more CoAs assigned to the respective interfaces to use the CoAs, enabling switching between the CoAs depending on the state of each interface. Non-Patent Document 2 cited below describes a technique for allowing a MN to register, with a HA, two or more CoAs in association with one HoA.
On the other hand, when a HA receives the registration of two or more CoAs from a MN, the HA can select a CoA based on the intention of the MN if the HA can acquire, from the MN, information (flow control information, Routing Rule) for determining which CoA should be used as the destination of packets destined to the HoA of the MN.
For example, Non-Patent Document 3 cited below describes a technique for causing a MN to register flow control information with a HA as a technique for enabling the HA to select a CoA according to the flow. This flow control information includes flow information (Routing Filter) consisting of pieces of information (5-tuple) such as a destination address, a source address, a destination port number, a source port number, and a protocol number, and a flow to be identified is represented by one or more pieces of information, or a combination of all pieces of information. The flow control information also includes information in which a flow ID for identifying each piece of flow information is associated with a CoA (or a Binding Unique Identifier (BID) for identifying the CoA) used as a destination. The flow ID may be information for identifying an actual flow. If desiring to set a specific IF as a forwarding destination for a certain flow, the MN notifies the HA of flow control information including a flow ID for identifying the flow and a CoA assigned to an IF desired to be set as the forwarding destination of this flow or a BID for identifying the CoA.
Further, if the flow control information is notified from the MN, the HA receiving the registration of two or more CoAs forwards packets according to the flow control information. However, if the flow control information is not notified from the MN, the HA can switch CoAs as forwarding destinations according to its path selection policy. In this case, the HA can consider the connection conditions of the MN, communication path conditions and the conditions of communication with other nodes to select a CoA to which packets addressed to the MN are to be sent, so that the HA can switch over to a path more effective and suited to the conditions the HA can figure out.
Further, in Non-Patent Document 4 cited below, Proxy Mobile IP (PMIP, e.g., Proxy Mobile IPv6) is defined as a network-based mobility control protocol. PMIP is a technique for performing the mobility management of the MN on the network side to eliminate the need for the MN to perform processing for mobility control. Each network in a domain (PMIP domain) providing PMIP is configured to advertise the same home prefix to a specific MN at all times, so that any MN changing its network connection does not need to change its address, enabling the MN to act simply as an IPv6 node without the need to be aware of the presence of a HA.
On the other hand, on the network side, a Mobile Access Gateway (MAG) performs mobility control as a proxy node of the MN not only to advertise the home prefix to the MN, but also to register, with a Local Mobility Anchor (LMA), its address (or its prefix) as location information on the destination of the MN. The LMA manages the location information on the MN in the PMIP domain, and corresponds to a HA in mobile IP. Thus, packets destined to the home address of the MN are intercepted by the LMA, forwarded from the LMA to the MAG, and further sent from the MAG to the MN.    Non-Patent Document 1: D. Johnson, C. Perkins, J. Arkko, “Mobility Support in IPv6,” RFC3775, June 2004.    Non-Patent Document 2: R. Wakikawa, T. Ernst, K. Nagami, “Multiple Care-of Addresses Registration,” draft-ietf-monami6-multiplecoa-03.txt, July 2007.    Non-Patent Document 3: H. Soliman, N. Montavont, N. Fikouras, K. Kuladinithi, “Flow Bindings in Mobile IPv6 and Nemo Basic Support,” draft-soliman-monami6-flow-binding-04.txt, February 2007.    Non-Patent Document 4: S. Gundavelli, K. Leung, V. Devarapalli, “Proxy Mobile IPv6,” draft-sgundave-mipv6-proxymipv6-00, October 2006.
However, in the case of use of the technique as shown in Non-Patent Document 3 mentioned above, in which the MN registers, with the HA, flow control information for specifying the forwarding destination of a flow, the MN has to register, with the HA, flow control information on all flows each specifying a specific IF as the forwarding destination.
For example, upon receiving a flow related to communication originated from a Correspondent Node (CN), if the MN wants the flow to be forwarded to a specific IF, the MN registers, with the HA, flow control information for specifying the forwarding destination of the flow. Similarly, upon starting communication with the CN, if the MN wants a flow sent from the CN in connection with the communication to be forwarded to a specific IF, the MN also needs to register flow control information for specifying the forwarding destination of the flow.
Thus, the MN has to register, with the HA, flow control information on each flow whose forwarding destination the MN wants to specify. Therefore, as the number of flows whose forwarding destinations the MN wants to specify increases, the number of pieces of flow control information registered by the MN increases. The increase in the number of flows poses a problem of dramatically increasing the load on the HA for forwarding destination control and the load on the MN for registration of flow information.
Further, since the number of registration messages sent from the MN to register the flow control information and the number of messages as responses to the registration messages increase, the network traffic increases, causing a potential problem of packet loss or delay.